If you’re involved in a lawsuit that is moving toward trial, you might find your lawyer or the opposition’s legal representation pushing for the use of expert witness testimony. For those who haven’t dealt with many expert witnesses before, understanding what this role involves and how expert testimony can be a turning point in a case is very important. Here are three of the most important things to know if you’ve never been involved with a case that uses them before.

1. Expert Witnesses Are Called To Discuss Professional Conclusions

Most of the time, witnesses are prohibited from simply testifying to their opinions or interpretations of events. That’s because the jury, or in some cases the judge, is expected to draw those conclusions. The rules change around expert witnesses, however, because they are called to provide professional analysis about a complex issue they have specific training and experience working with. Some examples include:

• A finance expert witness explaining and providing context for forensic accounting analysis
• A medical expert speaking to a diagnosis or physiological phenomenon related to the case
• Physical evidence experts discussing calculations related to ballistics or other complex investigative fields

2. Experts Can Be Called in Civil or Criminal Cases

Criminal trials also allow for the use of expert witnesses, especially when refuting the state’s conclusions about the outcome of an investigation. Many witnesses have more experience with civil cases because so many criminal cases are settled via a plea, but there are some who specialize in criminal cases exclusively.

3. Rules About Expert Testimony Vary By Jurisdiction

Some jurisdictions, like the federal court system, require a separate hearing to qualify an expert. Others allow a judge to make a determination on the spot when the expert is added to a witness list, based on an attorney’s presentation of the witness’s experience and credentials. Understanding these rules for the jurisdiction of any given case is vital to using them as a resource, so experts are not called in on an impulse. Their inclusion is carefully considered as part of a larger legal strategy.